rudiments

The rudiments of something are the basics of it. The equation 2 + 2 = 4 is one of the rudiments of arithmetic.

When you're talking about the rudiments, you're talking about the most simple elements of something. In any introductory course, you're going to learn the rudiments of a subject. For example, Psychology 101 will teach the rudiments of psychology. For very complex subjects — like nuclear physics — even the rudiments might be hard for the average person to understand. But if you don't master the rudiments first, you're not going to get very far.